如何在firebug中调试ajax响应

My function is like this when function call at that time it's automatically refresh page I can not see that response in firebug this function is working properly but I can't see output in firebug

<script>
function getQty(itemId)
{
  var dataString = "itemId=" + itemId;

  $.ajax({
    type:"GET",
    url:"allQty.php",
    data: dataString,
    success:function(data)
    {
      $('.totalQty').html(data)
    }
  });
}
</script>

here call function

<a href="screen.php?{$a}&itemId={$itemArray[sec].itemId}" class="btn itemId" id="{$itemArray[sec].itemId}" name="itemId" onClick="getQty(this.id);">{$itemArray[sec].itemNm}</a>

Set "Persist" ON in Network tab in Firebug or "Preserve log" in Chrome